A polysilazane is well known as a compound useful for a precursor of silicon nitride (for example, see Patent literature 1 below). In recent years, it has also attracted attention as a material for forming an insulation film such as an interlayer insulation film, a passivation film, a protective film, a planarization film, and the like of the electronic device such as a semiconductor device. These films are formed by applying a coating liquid containing a polysilazane to an appropriate substrate, followed by baking to transform the polysilazane to a siliceous film (for example, see Patent literatures 2 to 5 below).
In addition, in the electronic device such as a semiconductor device, a semiconductor element such as a transistor, a resistor, etc. are arranged on a substrate and for electrically isolating and separating these elements, an isolation region which is composed of an insulation film is formed between the elements by using a polysilazane. Furthermore, in the field of the electronic devices, densification and high integration of the elements have been proceeded and in order to cope with these densification and high integration, a trench isolation structure, which is produced by forming a fine groove on a surface of a semiconductor substrate and filling the groove with an insulating material to electrically separate between elements formed at both sides of the groove, has been adopted.
A coating liquid containing a polysilazane is used also in the aforementioned trench isolation structure. As a polysilazane used for forming insulation films including the trench isolation structure, passivation films, planarization films, protective films etc., there is exemplified, in Patent document 1, an inorganic polysilazane having a repeating unit represented by the following formula;

As a synthesis method of a polysilazane, Patent document 1 discloses a method in which adducts of dihalosilane with a base are reacted with ammonia. In addition to this, various other methods have been proposed for synthesizing a polysilazane, for example, (a) a method of reacting a silicon halide such as SiCl4, SiH2Cl2 or the like with an amine, (b) a method of producing a polysilazane from a silazane by use of a dehydrogenating catalyst consisting of an alkali metal hydride such as KH, (c) a method of synthesizing a silazane by a dehydrogenation reaction of a silane compound with an amine compound by use of a transition metal complex catalyst, (d) a method of performing an amine exchange of aminosilane with ammonia by use of an acid catalyst such as CF4SO3H, (e) a method of performing an amine exchange of an aminosilane with a large amount of ammonia or amine, (f) a method of performing an amine exchange reaction of a polyvalent aminosilane with a polyhydrogenated nitrogen-containing compound in the presence of a basic catalyst, etc. (for example, see Patent document 6).
By the way, various properties such as an insulation property, a flatness of a film, a resistance for an acid, an alkali, a solvent, and the like, a high barrier property, and so on are required for the insulation film, the passivation film, the protective film, the planarization film, and the like in the electronic device such as the semiconductor device. Though a film fulfilling these properties can be produced by the aforementioned method for forming a siliceous film with a coating liquid containing a polysilazane, shrinkage of the film and a generation of a residual stress arise upon baking a polysilazane to convert into a siliceous film. When the shrinkage or residual stress of the film is large, there occur problems like that cracks and a crystal defect of the substrate. For this reason, a polysilazane which shrinkage and residual stress are suppressed as much as possible, are expected. In addition, it is desirable to form a high density siliceous film in order to obtain good etching properties in the trench isolation structure.